Transducer head temperature monitoring

ABSTRACT

Changes in the thermal boundary condition near a close point of an ABS to a media indicate proximity of the ABS with the media. Before contact, heat conduction from the ABS is primarily through convective and/or ballistic heat transfer to air between the ABS and the media. After contact, heat flux primarily flows from the ABS to the media through solid-solid conductive contact. Further, a light source within a HAMR transducer head may create additional thermal variations within the transducer head. These thermal variations create temperature variations within the transducer head. Two resistance temperature sensors on the transducer head at varying distances from the close point and/or light source measure these temperature variations. A temperature difference between the two resistance temperature sensors indicates proximity of the close point to the media and/or light output.

SUMMARY

Implementations described and claimed herein provide a transducer headcomprising two temperature sensors at two disparate distances from aclose point of the transducer head with a media. A difference betweentemperatures of each of the two temperature sensors indicates proximityof the transducer head to the media at the close point.

Other implementations are also described and recited herein.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1A illustrates an example transducer head not in contact with amedia, having a first resistance temperature sensor at or near a closepoint and a second resistance temperature sensor spaced away from theclose point.

FIG. 1B illustrates an example transducer head in contact with a media,having a first resistance temperature sensor at or near a close pointand a second resistance temperature sensor spaced away from the closepoint.

FIG. 2A illustrates an example transducer head having a first resistancetemperature sensor spaced away from an un-powered laser diode and asecond resistance temperature sensor at or near the un-powered laserdiode.

FIG. 2B illustrates an example transducer head having a first resistancetemperature sensor spaced away from a powered laser diode and a secondresistance temperature sensor at or near the powered laser diode.

FIG. 3A illustrates an example transducer head not in contact with amedia, having a first resistance temperature sensor spaced away from anun-powered laser diode and at or near a close point and a secondresistance temperature sensor at or near the un-powered laser diode andspaced away from the close point.

FIG. 3B illustrates an example transducer head in contact with a media,having a first resistance temperature sensor spaced away from a poweredlaser diode and at or near a close point and a second resistancetemperature sensor at or near the powered laser diode and spaced awayfrom the close point.

FIG. 4 illustrates a plan view of an example actuator assembly with adetail view of a transducer head with differential resistancetemperature sensors according to the presently disclosed technology.

FIG. 5 illustrates a plan view of an example transducer head depositedon a trailing surface of a slider including a pair of differentialresistance temperature sensors.

FIG. 6 illustrates a sectional isometric view of the example transducerhead of FIG. 3 at Section A-A.

FIG. 7 illustrates a plan view of an example HAMR transducer headdeposited on a trailing surface of a slider including a pair ofdifferential resistance temperature sensors.

FIG. 8 illustrates a first example sectional isometric view of theexample HAMR transducer head of FIG. 6 at Section A-A.

FIG. 9 illustrates a second example sectional isometric view of theexample HAMR transducer head of FIG. 6 at Section A-A.

FIG. 10 illustrates example operations for mapping surface contours on amedia using transducer head temperature monitoring.

FIG. 11 illustrates example operations for detecting light output in aHAMR transducer head using transducer head temperature monitoring.

DETAILED DESCRIPTIONS

Contact detection technologies are used for commissioning or periodicadjustment operations that set flying height of a thin film transducerhead in moving-media data storage systems (e.g., rotating magneticand/or optic disc drives). The flying height is defined as the spacingbetween the surface of a spinning storage media and the lowest point onthe slider assembly (i.e., the close point) in the data storage systems.A smaller flying height results in optimized performance of the datastorage systems. More specifically, higher contact detectionrepeatability enables lower active clearance and thus higher recordingdensity. Further, higher contact detection sensitivity reduces wear andoptimizes reliability of the data storage systems.

Some contact detection technologies in moving-media data storage systemsutilize one or more vibration sensors incorporated on or near theslider. When the slider contacts a corresponding storage media,vibration amplitude of the slider changes and the vibration sensor(s)detect the contact.

In addition to detecting vibration, the presently disclosed technologyuses changes in the thermal boundary condition near a close point of anair-bearing slider (ABS) upon proximity and/or contact with a movingdata storage media to detect proximity and/or contact of the ABS withthe media. Before contact, heat conduction from the ABS is primarilythrough convection and/or ballistic heat transfer to the air in the gapbetween a transducer head on the ABS and the media. After contact, heatflux primarily flows from the transducer head to the media throughsolid-solid conductive contact and/or a close proximity effect at theclose point. This is because solid-solid contact and/or two solids invery close proximity to one another have a higher thermal conductivitycompared to solid-air convection or ballistic heat transfer. Inaddition, after contact, friction-induced heating where the close pointmeets the media may contribute to changes in the thermal boundarycondition.

As a result, the thermal boundary condition at the close point of theABS as compared to elsewhere on the ABS varies depending on whether theclose point of the ABS is in contact with the media or not. Thesethermal boundary condition variations create temperature variations onthe ABS. In one specific implementation, the close point is cooler thanother points on the ABS spaced away from the close point when in closeproximity to the media. In another implementation, the close point iswarmer than other points on the ABS spaced away from the close pointupon contact with the media.

Measurements of these temperature variations have a DC componentassociated with an average fly height change and an AC componentassociated with vertical modulation of the ABS as it flies over themedia. The presently disclosed technology focuses in part onimplementing two resistance temperature sensors on an ABS, one near theclose point and one spaced away from the close point. A temperaturedifference between the two resistance temperature sensors indicatesproximity and/or contact of the close point with the media. The tworesistance temperature sensors may detect the DC and/or AC temperaturevariations and may be implemented on modulating or non-modulatingsliders.

The presently disclosed technology may also be used to measure output ofa light source (e.g., a laser diode), output of a heater, and/orhead-media spacing (HMS) in a “heat assisted magnetic recording” storagesystem. “Heat assisted magnetic recording,” optical assisted recordingor thermal assisted recording (collectively hereinafter HAMR), generallyrefers to locally heating a recording medium to reduce the coercivity ofthe recording medium so that an applied magnetic writing field can moreeasily affect magnetization of the recording medium during a temporarymagnetic softening of the recording medium caused by the local heating.HAMR allows for the use of small grain media, which allows for recordingat increased areal densities, with a larger magnetic anisotropy at roomtemperature assuring a sufficient thermal stability. HAMR can be appliedto any type of storage media, including for example, tilted media,longitudinal media, perpendicular media, and/or patterned media.

Effective HAMR relies on precise local heating of the recording medium.The presently disclosed technology may be used to monitor the output ofthe light source used to heat the recording medium. Further, thepresently disclosed technology may be used to monitor the heat output ofa heater on the HAMR recording head. Still further, the presentlydisclosed technology may measure HMS between the HAMR recording head andthe recording media.

FIG. 1A illustrates an example transducer head 102 (not in contact witha media 104), having a first resistance temperature sensor 106 at ornear a close point 108 and a second resistance temperature sensor 110spaced away from the close point 108. The surface of the transducer head102 facing the media 104 is often slightly convex (shown exaggerated forillustrative purposes), thus yielding the close point 108 (as comparedto other points on the surface of the transducer head 102) facing themedia 104. Heat-transfer arrows (e.g., arrow 112) illustrate heatconduction from the transducer head 102 primarily through convectiveand/or ballistic heat transfer to the air in the gap between thetransducer head 102 and the media 104. Temperature sensors 106, 110 arespecifically configured to detect contact of the close point 108 of thetransducer head 102 with the media 104.

The first resistance temperature sensor 106 has a resistance symbolizedby R₁ (not shown) and is located at or near the close point 108, whichin many implementations is near a write pole (not shown) on thetransducer head 102. The second resistance temperature sensor 110 has aresistance symbolized by R₂ (not shown) and is spaced away from theclose point 108, which in many implementations is near a reader (notshown) on a transducer head 102. In one implementation, the secondresistance temperature sensor 110 is merely 2-30 micrometers away fromthe first resistance temperature sensor 106. However, other distancesbetween the first resistance temperature sensor 106 and secondresistance temperature sensor 110 are contemplated herein.

In one implementation, the resistances of the first and secondresistance temperature sensors 106, 110 are equal at the sametemperature. Current source I₁ powers the first sensor 106 and currentsource I₂ powers the second sensor 110. During a calibration procedure,a user monitors voltage (V) between terminals A and B and adjusts aratio between I₁ and I₂ until V=I₂R₂−I₁R₁=0. In an alternativeimplementation, there is a known resistance differential (or difference)between the first and second resistance temperature sensors 106, 110. Ina further implementation, voltage (V) is calibrated to a non-zeromagnitude.

FIG. 1B illustrates an example transducer head 102 in contact with amedia 104, having a first resistance temperature sensor 106 at or near aclose point 108 and a second resistance temperature sensor 110 spacedaway from the close point 108. Heat-transfer arrows (e.g., arrow 114)illustrate heat flux primarily flowing from the transducer head 102 tothe media 104 through solid-solid conductive contact at the close point108. Temperature sensors 106, 110 are configured to detect contact ofthe close point 108 of the transducer head 102 with the media 104.

Close proximity of the close point 108 with the media 104 may dissipateadditional heat from the transducer head 102. Further, contact of theclose point 108 with the media 104 may generate additional heat in thetransducer head 102. Both heat-dissipation and heat-generation at theclose point 108 is referred to herein as a heat variation source.Further, the contact and/or proximity of the transducer head 102 withthe media 104 is referred to herein as a performance metric.

When the transducer head 102 is active and the close point 108 isbrought into contact with the media 104 as shown moving from FIG. 1A toFIG. 1B, a temperature change for resistance temperature sensor 106(ΔT₁) and a temperature change for resistance temperature sensor 110(ΔT₂) occurs. A voltage (V) between terminals A and B is defined byV=I₂R₂(1+cΔT₂)−I₁R₁(1+cΔT₁)=cI₁R₁(ΔT₂−ΔT₁), wherein c is the temperaturecoefficient of resistance. As the close point 108 is brought closer tothe media 104, but before contact, ΔT₁ is very close to ΔT₂ and Vapproximately equals zero. After contact (see FIG. 2A), ΔT₂ becomesdifferent than ΔT₁ because additional heat is conducted away from theclose point 108 into the media 104 via solid-solid contact, a closeproximity effect, and/or friction-induced heat is generated at the closepoint. As a result, voltage (V) becomes significantly greater than zeroand indicates contact.

In some implementations, noises created by ambient temperaturevariation, heater power, write coil power, reader current, mechanicalvibrations, and/or electronic signals make the difference between ΔT₁and ΔT₂ difficult to measure. By using a modulated sensing method,noises that are at frequencies different from the modulation frequencymay be eliminated. In one implementation, a heater power (discussed inmore detail below) is modulated at a certain frequency with constant I₁and I₂ current using a thermal actuation controller. For example, theheater power is modulated at a frequency of 100 Hz while I₁ and I₂ bothapproximately equal 1 mA DC. In another implementation, I₁ and I₂ aremodulated at a synchronized frequency using a current modulator whilethe heater power is constant. In either implementation, a lock-intechnique is used to analyze the voltage (V). For example, software orhardware such as commercial integrated circuit demodulators performlock-in signal demodulation of voltage (V).

FIG. 2A illustrates an example transducer head 202 having a firstresistance temperature sensor 206 spaced away from an un-powered laserdiode 244 and a second resistance temperature sensor 210 at or near theun-powered laser diode 244. The surface of the transducer head 202facing a media 204 is often slightly convex (shown exaggerated forillustrative purposes), thus yielding a close point 208 (as compared toother points on the surface of the transducer head 202) facing the media204. The temperature sensor 206 and temperature sensor 210 are separatedby a return pole 236, which at least partially isolates the temperaturesensor 206 from heat generated by the laser diode 244 when the laserdiode 244 is in operation. In this implementation, the temperaturesensors 206, 210 are equidistant from the close point 208. Therefore,convective and/or ballistic heat transfer to the air in the gap betweenthe transducer head 1202 and the media 204 should affect temperaturesensors 206, 210 equally. Temperature sensors 206, 210 are configured todetect heat output of the laser diode 244.

The first resistance temperature sensor 206 has a resistance symbolizedby R₁ and is spaced away from the laser diode 244. Temperature sensor206 in many implementations is adjacent a return pole (not shown) on aside opposite from the laser diode 244, on the transducer head 202. Thesecond resistance temperature sensor 210 has a resistance symbolized byR₂ and is located at or near the laser diode 244, which in manyimplementations is also adjacent the return pole (not shown), however onthe same side of the return pole as the laser diode 244 on thetransducer head 202. In one implementation, the second resistancetemperature sensor 210 is merely 2-30 micrometers away from the firstresistance temperature sensor 206. However, other distances between thefirst resistance temperature sensor 206 and second resistancetemperature sensor 210 are contemplated herein.

In one implementation, the resistances of the first and secondresistance temperature sensors 206, 210 are equal at the sametemperature. Current source I₁ powers the first sensor 206 and currentsource I₂ powers the second sensor 210. During a calibration procedure,a user monitors voltage (V) between terminals A and B and adjusts aratio between I₁ and I₂ until V=I₂R₂−I₁R₁=0. In an alternativeimplementation, there is a known resistance difference between the firstand second resistance temperature sensors 206, 210. In a furtherimplementation, voltage (V) is calibrated to a non-zero magnitude.

FIG. 2B illustrates an example transducer head 202 having a firstresistance temperature sensor 206 spaced away from a powered laser diode244 and a second resistance temperature sensor 210 at or near thepowered laser diode 244. Heat-transfer arrows (e.g., arrow 246)illustrate heat flux primarily flowing from the laser diode 244 to thesecond resistance temperature sensor 210. Temperature sensors 206, 210are configured to detect heat output of the laser diode 244.

The powered laser diode 244 and/or any paths from the powered laserdiode 244 to the media are referred to herein as a heat variationsource. Further, the light and/or heat output of the powered laser diode244 and/or any paths from the powered laser diode 244 to the media 204are referred to herein as a performance metric.

When the laser diode 244 is powered as shown moving from FIG. 2A to FIG.2B, a temperature change for the resistance temperature sensor 206 (ΔT₁)and the resistance temperature sensor 210 (ΔT₂) occurs. A voltage (V)between terminals A and B is defined by V=I₂R₂(1+cΔT₂)−I₁R₁(1+cΔT₁)=cI₁R₁(ΔT₂−ΔT₁), wherein c is the temperaturecoefficient of resistance. As the close point 108 is moved closer and/orfurther from the media 104, but before the laser diode 244 is powered(see FIG. 1A), ΔT₁ is very close to ΔT₂ and V approximately equals zero.After the laser diode 244 is powered (see FIG. 2A), ΔT₂ becomesdifferent from ΔT₁ because more heat is conducted to the secondresistance temperature sensor 210 than the first resistance temperaturesensor 206. As a result, voltage (V) becomes significantly greater thanzero and is a metric of the magnitude of heat generated by the laserdiode 244.

In some implementations, noises created by ambient temperaturevariation, heater power, write coil power, reader current, mechanicalvibrations, and/or electronic signals make the difference between ΔT₁and ΔT₂ difficult to measure. By using a modulated sensing method,noises that are at frequencies different from the modulation frequencymay be eliminated. In one implementation, heater power (discussed inmore detail below) is modulated at a certain frequency with constant I₁and I₂ current using a thermal actuation controller. For example, theheater power is modulated at a frequency of 100 Hz while I₁ and I₂ bothapproximately equal 1 mA DC. In another implementation, I₁ and I₂ aremodulated at a synchronized frequency using a current modulator whilethe heater power is constant. In either implementation, a lock-intechnique is used to analyze the voltage (V). For example, software orhardware such as commercial integrated circuit demodulators performlock-in signal demodulation of voltage (V).

FIG. 3A illustrates an example transducer head 302 not in contact with amedia 304, having a first resistance temperature sensor 306 spaced awayfrom an un-powered laser diode 344 and at or near a close point 308 anda second resistance temperature sensor 310 at or near the un-poweredlaser diode 344 and spaced away from the close point 308. Temperaturesensors 306, 310 are oriented in a manner that is both capable ofdetecting contact of the close point 308 of the transducer head 302 withthe media 304 as disclosed with respect to FIG. 1A and detecting heatoutput of the laser diode 344 as disclosed with respect to FIG. 2A.

FIG. 3B illustrates an example transducer head 302 in contact with amedia 304, having a first resistance temperature sensor 306 spaced awayfrom a powered laser diode 344 and at or near a close point 308 and asecond resistance temperature sensor 310 at or near the powered laserdiode 344 and spaced away from the close point 308. By holding the laserdiode 344 in a constant powered or unpowered state and bringing theclose point 308 in contact with the media 304, the contact may bedetected by a spike in the temperature of the first resistancetemperature sensor 306 as compared to the second resistance temperaturesensor 310, as disclosed in detail with respect to FIGS. 1A and 1B.Further, by holding the transducer head 302 at a constant distance fromthe media 304, the heat output of the laser diode 344 may be detected bycomparing the temperature of the first resistance temperature sensor 306with the temperature of the second resistance temperature sensor 310, asdisclosed in detail with respect to FIGS. 2A and 2B.

Close proximity of the close point 308 with the media 304 may dissipateadditional heat from the transducer head 302. Further, contact of theclose point 308 with the media 304 may generate additional heat in thetransducer head 302. Still further, the laser diode 344 may generateadditional heat in the transducer head 302. Both heat-dissipation andheat-generation at the close point 308 as well as heat-generation at thelaser diode 344 and/or any paths from the laser diode 344 to the media304 are referred to herein as a heat variation source. Further, thecontact and/or proximity of the transducer head 302 with the media 304and the light and/or heat output of the powered laser diode 344 and/orany paths from the powered laser diode 344 to the media 304 is referredto herein as a performance metric.

FIG. 4 illustrates a plan view of an example actuator assembly 416 witha detail view of a transducer head 402 with differential resistancetemperature sensors according to the presently disclosed technology. Theactuator assembly 416 includes one or more actuator arms (e.g., actuatorarm 418) with one or more flexures (e.g., flexure 420) extending fromeach of the actuator arms, generally in the y-direction. Mounted at thedistal end of each of the flexures is a transducer head (e.g., head 402)that includes an air-bearing slider (e.g., slider 422) enabling thetransducer head to fly in close proximity above the correspondingsurface of an associated media. The actuator assembly 416 with thetransducer head 402 of FIG. 4 is shown from a perspective looking upfrom the media.

Each slider incorporates air-bearing features (e.g., features 424) tocontrol the aerodynamic interaction between the slider and the mediathere under. This aerodynamic interaction sets and controls fly heightof the transducer head 402. Microelectronics (such as those shown indetail in FIGS. 5-9), including differential resistance temperaturesensors, are mounted on a trailing edge of each slider. In otherimplementations, the microelectronics are mounted on a leading edge orside edge of each slider. The microelectronics are separated from eachslider and sealed from the environment by layers of dielectric material(e.g., dielectric 426). The microelectronics may also be mounted on anair-bearing feature, or elsewhere on each slider.

FIG. 5 illustrates a plan view of an example transducer head 502deposited on a trailing surface of a slider 522 including a pair ofdifferential resistance temperature sensors 506, 510. The transducerhead 502 includes various microelectronic components for reading andwriting information to and from a storage media (i.e., a reader 528, awriter 530, a first reader shield 532, a second reader shield 534, afirst return pole 536, a second return pole 538, and a heater 548) whichare mounted on a substrate 540 and separated by dielectric material 526.The microelectronic components are also separated from an externalenvironment by the dielectric material 526. In other implementations,additional microelectronic components may be deposited on the slider522. The transducer head 502 is not shown to scale in FIG. 5. In manyimplementations, thickness in the y-direction is very small with respectto the width in the x-direction of the substrate 540, themicroelectronic components, and/or the dielectric material 526.

The transducer head 502 may be installed onto the slider 522 using anyof a variety of microelectronic fabrication techniques. Often themicroelectronic components are deposited onto the substrate 540 usingone or more thin films. The thin films may be patterned to give thelayers distinctive features or form openings in the layers. The thinfilms may also include the dielectric material 526 to separate themicroelectronic components. Further, the thin films may also be etchedto remove some undesirable portions of the thin films or the substrate540. Still further, the thin films and/or substrate 540 may be furthermodified using processes including, but not limited to doping (usingthermal diffusion and/or ion implantation),micro-cutting/micro-fabrication, chemical-mechanical planarization,wafer cleaning or other surface preparation, and wire bonding.

In an implementation where the microelectronic components aremanufactured using deposition, the dielectric material 526 is firstdeposited on the substrate 540. The dielectric material 526 is typicallya non-conductive material that serves to bond the microelectroniccomponents to the substrate 540 and/or anchor the microelectroniccomponents within the dielectric material 526. The dielectric material526 may also fill gaps between various microelectronic components andmay encompass the microelectronic components to protect them from damagefrom an external environment (e.g., physical impact, contaminants, andoxidation).

Moving in the y-direction, the first reader shield 532 is deposited onthe dielectric material 526. The reader 528 and second resistancetemperature sensor 510 are deposited on the first reader shield 532 andthe second reader shield 534 is deposited on the reader 528 and thesecond resistance temperature sensor 510. The reader shields 532, 534may serve to electrically and/or magnetically isolate the reader 528from other components of the transducer head 502 (e.g., the writer 530).Layers of dielectric material 526 separate two or more of the reader528, reader shields 532, 534, and second resistance temperature sensor510. In some implementations, one or both reader shields 532, 534 arenot present. In another implementation, the first resistance temperaturesensor 506 is installed in a post-deposition processing step.

Still moving in the y-direction, the first return pole 536 is depositedwith a layer of dielectric material 526 separating the second readershield 534 from the first return pole 536. The writer 530 and the firstresistance temperature sensor 506 are deposited on the first return pole536 and the second return pole 538 is deposited on the writer 530 andthe first resistance temperature sensor 506. Layers of dielectricmaterial 526 separate each of the writer 530, first resistancetemperature sensor 506, and return poles 536, 538. In someimplementations, one or both return poles 536, 538 are not present. Inanother implementation, the first and/or second resistance temperaturesensors 506, 510 are installed in post-deposition processing. The heater548 is deposited adjacent to the second return pole 538. The heater 548is adapted to expand when powered, thereby pushing one or moremicroelectronic components closer to a storage media (not shown).

The dielectric material 526 covers the second return pole 538 and sealsthe microelectronic components from an external environment. Thedielectric material 526 may comprise one material for all areas of thetransducer head 502 or it may comprise different materials for layers ofdielectric material 526 adjacent the substrate 540, between themicroelectronic components, and/or sealing the microelectroniccomponents from the external environment. Magnetic flux flows from thewriter 530 to the storage media in close proximity to the writer 530 andback through one or both of the return poles 536, 538 in order to writebits of data to the media.

The resistance temperature sensors 506, 510 may be located elsewhere onthe transducer head 502 and/or slider 522 so long as one resistancetemperature sensor is closer to a close point (discussed in detailbelow) than the other resistance temperature sensor. The resistancetemperature sensors 506, 510 may be of any type including but notlimited to carbon resistors, thermistors, film thermometers, wire-woundthermometers, and coil elements. Further, the resistance temperaturesensors 506, 510 are often made of platinum. However, other materialswith a generally linear temperature-resistance relationship may also beused for the resistance temperature sensors 506, 510. In still otherimplementations, thermocouples may be used in place of the resistancetemperature sensors 506, 510.

FIG. 6 illustrates a sectional isometric view of the example transducerhead 502 of FIG. 5 at Section A-A. FIG. 6 is for illustrative purposesonly and does not indicate scale of any of the depicted microelectroniccomponents (i.e., a reader (not shown), a writer (not shown), a firstreader shield 632, a second reader shield 634, a first return pole 636,a second return pole 638, a first resistance temperature sensor 606, asecond resistance temperature sensor 610 and/or a heater 648) comprisinga transducer head 602 with respect to a slider 622 and/or a storagemedia 604. For example, the thickness of the microelectronic componentsand dielectric material 626 in the y-direction may be exaggerated withrespect to the width in the x-direction and height in the z-direction ofthe microelectronic components and the dielectric material 626.

As described in detail with respect to FIG. 5, moving in they-direction, FIG. 6 depicts dielectric material 626 deposited on asubstrate 640. The first reader shield 632 is deposited on thedielectric material 626. The reader (not shown) as well as the secondresistance temperature sensor 610 are deposited adjacent the firstreader shield 632. The second reader shield 634 is deposited adjacentthe reader (not shown) and the second resistance temperature sensor 610.One or more layers of dielectric material 626 separates the reader (notshown), second resistance temperature sensor 610, first reader shield632, and/or second reader shield 634 from one another.

Still moving in the y-direction, dielectric material 626 separates thesecond reader shield 634 from a first return pole 636. The writer (notshown) as well as a first resistance temperature sensor 606 aredeposited adjacent the first return pole 636. The second return pole 638is deposited adjacent the writer (not shown) and the first resistancetemperature sensor 606. One or more layers of dielectric material 626separate the writer (not shown), first resistance temperature sensor606, first return pole 636, and/or second return pole 638 from oneanother. The dielectric material 626 covers the second return pole 638and seals the microelectronic components from the environment. In someimplementations, portions of the microelectronic components facing themedia 604 are left exposed.

Typically, one or more of the microelectronic components are positionedcloser to the media 604 than other microelectronic components (i.e., aclose point 608). For example, in many implementations the writer (notshown) is positioned closer to the media 604 than the reader (not shown)is. Further, the first resistance temperature sensor 606 is positionedcloser to the close point 608 than the second resistance temperaturesensor 610. The variations in distance may be caused by a curvature ofthe surface of transducer head 602 facing the media 604 as shown in FIG.6. Further, some microelectronic components (e.g., the writer (notshown) may extend out of the transducer head 602 toward the media 604,instead of or in addition to the effect of curvature of the surface oftransducer head 602 facing the media 604. Distance 642 illustrates a flyheight difference between the close point 608 of the transducer head 602where the first resistance temperature sensor 606 is approximatelylocated and a point spaced away from the close point 608 where thesecond resistance temperature sensor 610 is located. The resistancetemperature sensors 606, 610 may be located elsewhere on the transducerhead 602 and/or slider 622 so long as one resistance temperature sensoris closer to the close point 608 than the other resistance temperaturesensor.

The transducer head 602 may also be equipped with a heater 648 attachedto or in close proximity to one or more of the microelectroniccomponents. The heater 648 is adapted to expand when powered, therebypushing one or more microelectronic components closer to the media 604(negative z-direction). For example, the heater 648 may push the firstreturn pole 636 closer to the media 604, make the first return pole 636the closest microelectronic component to the media 604, and thus makethe first return pole 636 the close point 608. Similarly, the heater 648can also contract when not powered or powered less to move the firstreturn pole 636 spaced away from the media 604 (positive z-direction).

In other implementations, the heater 648 is attached to or in closeproximity to one or more of the other microelectronic components (e.g.,the reader 628, the writer 630, the first reader shield 632, the secondreader shield 634, the second return pole 638, the first temperaturesensor 606, and/or the second temperature sensor 610) and moves theother microelectronic component(s) in the positive z-direction and/ornegative z-direction. In this implementation, one or more of the othermicroelectronic components attached to the heater 648 is the close point608.

In an example implementation, a DC component of heater power linearlyincreases from 20 mW to 100 mW while resistances (indicatingtemperature) of the first resistance temperature sensor 606 and secondresistance temperature sensor 610 are monitored. The resistance of thesecond resistance temperature sensor 610 increases linearly with theheater power over the entire heater power range because secondresistance temperature sensor 610 is located away from the close point608 and the thermal boundary condition at the second resistancetemperature sensor 610 does not substantially change as the close point608 comes in close proximity and subsequently in contact with the media604. In some implementations, there may be a modulating AC component ofthe heater power as well that modulates at a known frequency. A thermalactuation controller controls the DC and AC (if present) components ofthe heater power.

The resistance of the first resistance temperature sensor 606 similarlyincreases linearly with the heater power up to about 60 mW. Between 60mW and 80 mW, however, the resistance of the first resistancetemperature sensor 606 remains relatively unchanged, indicating that theclose point 608 is in close proximity with the media 604. An increase inthermal conductivity near the close point 608 compensates for theincreasing heater power and results in the relatively unchangedtemperature of the first resistance temperature sensor 606 between 60 mWand 80 mW of heater power.

Above 80 mW, the resistance of the first resistance temperature sensor606 resumes a linear increasing trend, indicating contact of the closepoint 608 with the media 604. Saturation of the thermal conductivity atthe close point 608 and additional friction-inducing heating caused bycontact with the media 604 causes the linear increasing trend ofresistance to resume above 80 mW. Close proximity and/or contact of theclose point 608 with the media 604 can be detected by monitoring athreshold difference between the change in resistance of the secondresistance temperature sensor 610 and the change in resistance of thefirst resistance temperature sensor 606.

FIG. 7 illustrates a plan view of an example HAMR transducer head 702deposited on a trailing surface of a slider 722 including a pair ofdifferential resistance temperature sensors 706, 710. The HAMRtransducer head 702 includes various microelectronic components forreading and writing information to and from a storage media (i.e., areader 728, a writer 730, a first reader shield 732, a second readershield 734, a first return pole 736, a second return pole 738, a laserdiode (not shown), a waveguide core 750, a near-field transducer 752,and a heater 748) which are mounted on a substrate 740 and separated bydielectric material 726. The microelectronic components are alsoseparated from an external environment by the dielectric material 726.In other implementations, additional microelectronic components may bedeposited on the slider 722. The transducer head 702 is not shown toscale in FIG. 7. In many implementations, thickness in the y-directionis very small with respect to the width in the x-direction of thesubstrate 740, the microelectronic components, and/or the dielectricmaterial 726.

The transducer head 702 may be installed onto the slider 722 using avariety of microelectronic fabrication techniques, as described indetail with respect to FIG. 5. Further, in one implementation, the firstreader shield 732, reader 728, second reader shield 734, first returnpole 736, and writer 730 are deposited on the dielectric material 726 asdescribed in detail with respect to FIG. 5. The waveguide core 750,which can serve as a path for light from a light source (not shown) andthe near-field transducer 752 are deposited adjacent the writer 730 witha layer of dielectric material 726 separating the writer 730 from thewaveguide core 750 and the near-field transducer 752. The second returnpole 738 is deposited adjacent the waveguide core 750 with the secondresistance temperature sensor 710 deposited between the second returnpole 738 and the waveguide core 750. The first resistance temperaturesensor 706 is deposited on the opposite side of the second return pole738, spaced away from the waveguide core 750.

The heater 748 is deposited adjacent to the second return pole 738. Theheater 748 is adapted to expand when powered, thereby pushing one ormore microelectronic components closer to a storage media (not shown).Layers of dielectric material 726 separate each of the writer 730,waveguide core 750, return pole 738, and heater 748. In someimplementations, one or both return poles 736, 738 are not present. Inanother implementation, the first and/or second resistance temperaturesensors 706, 710 are installed in post-deposition processing steps. Thedielectric material 726 covers the second return pole 738 and seals themicroelectronic components from an external environment.

In the HAMR transducer head 702 of FIG. 7, the laser diode (not shown),waveguide core 750, and near-field transducer 752 work together tolocally heat an area on a storage media (not shown). In oneimplementation, the laser diode produces a beam of light that isdirected to the near-field transducer 752 via the waveguide core 750.The near-field transducer 752 focuses the light on a desired location onthe storage media to locally heat the storage media so that less energyis required to shift the polarity of the storage media at the heatedspot. In some implementations, a light source other than a laser diodeis used for the HAMR transducer head 702 of FIG. 7.

The resistance temperature sensors 706, 710 may be located elsewhere onthe transducer head 702 and/or slider 722 so long as one resistancetemperature sensor is closer to the waveguide core 750 (and thus lightfrom the laser diode) than the other resistance temperature sensor. Theresistance temperature sensors 706, 710 may be of any type including butnot limited to carbon resistors, film thermometers, wire-wouldthermometers, and coil elements. Further, the resistance temperaturesensors 706, 710 are often made of platinum. However, other materialswith a generally linear temperature-resistance relationship may also beused for the resistance temperature sensors 706, 710. In still otherimplementation, thermocouples may be used in place of the resistancetemperature sensors 706, 710.

FIG. 8 illustrates a first example sectional isometric view of theexample HAMR transducer head 702 of FIG. 7 at Section A-A. FIG. 8 is forillustrative purposes only and does not indicate scale of any of thedepicted microelectronic components (i.e., a reader 828, a writer 830, afirst reader shield 832, a second reader shield 834, a first return pole836, a second return pole 838, a laser diode (not shown), a waveguidecore 850, a near-field transducer 852, a first resistance temperaturesensor 806, a second resistance temperature sensor 810 and/or a heater848) comprising a transducer head 802 with respect to a slider 822and/or a storage media 804. For example, the thickness of themicroelectronic components and dielectric material 826 in they-direction may be exaggerated with respect to the width in thex-direction and height in the z-direction of the microelectroniccomponents and the dielectric material 826.

As described in detail with respect to FIG. 7, moving in they-direction, FIG. 8 depicts dielectric material 826 deposited on asubstrate 840. The first reader shield 832 is deposited on thedielectric material 826. The reader 828 is deposited adjacent the firstreader shield 832 and the second reader shield 834 is deposited adjacentthe reader 828. One or more layers of dielectric material 626 separatesthe reader 828, first reader shield 832, and/or second reader shield 834from one another.

Still moving in the y-direction, dielectric material 826 separates thesecond reader shield 834 from the first return pole 836. The writer 830is deposited adjacent the first return pole 836. The waveguide core 850and the near-field transducer 852 are deposited adjacent the writer 830.A second return pole 838 is deposited with the second resistancetemperature sensor 810 between the second return pole 838 and thewaveguide core 850 and the first resistance temperature sensor 806 onthe side of the second return pole 838 spaced away from the waveguidecore 850. One or more layers of dielectric material 826 separate thewriter 830, waveguide core 850, near-field transducer 852, firstresistance temperature sensor 806, second resistance temperature sensor810, first return pole 836, and/or second return pole 838 from oneanother. The dielectric material 826 seals the microelectroniccomponents from the environment, however in some implementations;portions of the microelectronic components facing the media 804 are leftexposed.

The transducer head 802 may also be equipped with a heater 848 attachedto or in close proximity to one or more of the microelectroniccomponents. The heater 848 is adapted to expand when powered, therebypushing one or more microelectronic components closer to the media 804(negative z-direction). For example, the heater 848 may push the firstreturn pole 836 closer to the media 804. Similarly, the heater 848 canalso contract when not powered or powered less to move the first returnpole 836 spaced away from the media 804 (positive z-direction).

In an example implementation, light (illustrated by arrow 854) generatedby a laser diode (not shown) is transmitted through the HAMR transducerhead 802 via the waveguide core 850 to the near-field transducer 852.The near-field transducer 852 focuses the light onto a desired locationon the media 804 (illustrated by arrow 856). Resistance (indicatingtemperature) of the second resistance temperature sensor 610 measureslight output from the laser diode (not shown). The first resistancetemperature sensor 806 is positioned away from the waveguide core 850.As a result, the resistance (indicating temperature) of the firstresistance temperature sensor 806 much less or not at all affected bychanging output from the laser diode (not shown). Therefore, temperaturechances experienced by both the first resistance temperature sensor 806and the second resistance temperature sensor 610 may be filtered outyielding an accurate measure of light output from the laser diode (notshown).

FIG. 9 illustrates a second example sectional isometric view of theexample HAMR transducer head 702 of FIG. 7 at Section A-A. FIG. 9 is forillustrative purposes only and does not indicate scale of any of thedepicted microelectronic components (i.e., a reader 928, a writer 930, afirst reader shield 932, a second reader shield 934, a first return pole936, a second return pole 938, a laser diode (not shown), a waveguidecore 950, a near-field transducer 952, a first resistance temperaturesensor 906, a second resistance temperature sensor 910 and/or a heater948) comprising a transducer head 902 with respect to a slider 922and/or a storage media 904. For example, the thickness of themicroelectronic components and dielectric material 926 in they-direction may be exaggerated with respect to the width in thex-direction and height in the z-direction of the microelectroniccomponents and the dielectric material 926. Further, the depictedmicroelectronic components may be assembled as disclosed in detail withrespect to FIGS. 7 & 8.

In FIG. 9, the first resistance temperature sensor 906 and the secondresistance temperature sensor 910 are oriented on opposite sides of thesecond return pole 938, similar to the implementation of FIG. 8. As aresult, the second resistance temperature sensor 910 is significantlymore sensitive to temperature changes caused by light output from thelaser diode (not shown) than the first resistance temperature sensor906. The first resistance temperature sensor 906 is moved near the closepoint similar to the implementation of FIG. 6. As a result, the firsttemperature sensor 906 is significantly more sensitive to temperaturechanges caused by proximity and/or contact of the close point 908 withthe media 904 than the second resistance temperature sensor 910.

The configuration of the first resistance temperature sensor 906 and thesecond resistance temperature sensor 910 of FIG. 9 enables the HAMRtransducer head 902 to detect both close proximity and/or contact of theclose point 908 with the media 904 as described in detail with respectto FIG. 6 and light output from the laser diode (not shown) as describedin detail with respect to FIG. 8. More specifically, when the lightoutput from the laser diode is held at a constant value, the firstresistance temperature sensor 906 and the second resistance temperaturesensor 910 may be implemented to detect close proximity and/or contactof the close point 908 with the media 904. Further, when the heaterpower is held at a constant value, the resistance temperature sensor 906and the second resistance temperature sensor 910 may be implemented todetect light output from the laser diode (not shown).

FIG. 10 illustrates example operations 1000 for mapping surface contourson a media using transducer head temperature monitoring. For example,the operations 1000 may apply to the transducer head 102, 502, 602 andHAMR transducer head 302, 702, 902 implementations depicted in FIGS. 1A,1B, 3A, 3B, 5, 6, 7, & 9. In one implementation, a transducer head orHAMR transducer head (collectively a transducer head) for reading and/orwriting data from/to the media is equipped with two resistancetemperature sensors, one near a close point of the transducer head withthe media and the other a known distance away from the close point. In acalibration operation 1010, current applied to one or both of theresistance temperature sensors in a differential resistance circuit iscalibrated to yield a voltage difference of zero across the resistancetemperature sensors when the resistance temperature sensors are at thesame temperature. In an alternative implementation, the current appliedto one or both resistance temperature sensors is calibrated to yield aknown non-zero voltage difference across the resistance temperaturesensors.

In yet another implementation, a number of known factors are responsiblefor temperature variations in a transducer head (e.g., laser output (ina HAMR implementation), heater output, ambient drive temperature, writecoil output, reader current, proximity/contact of the transducer headwith the media). At least a laser diode, a heater, a write coil, areader, and a close point of the transducer head with the media arereferred to herein as a heat variation sources. At least the laseroutput (in a HAMR implementation), heater output, ambient drivetemperature, write coil output, reader current, proximity/contact of thetransducer head with the media are referred to herein as performancemetrics. In the calibration operation 1010, one or more of the knownfactors for temperature variation are mapped to determine theircontribution to a voltage difference across the resistance temperaturesensors during expected normal operation of the transducer head or HAMRtransducer head.

The natural roughness and/or surface contours on the media affect flyheight of the transducer head depending on its location over the media.In a moving operation 1020, the transducer head is moved over a selectedtrack sector or cluster on the media for mapping surface contours of theselected track sector or sectors. In other implementations, selectedtracks and/or geometrical sectors are used to map surface contours ofthe media.

In a heating operation 1030, heater power is linearly increased whilethe transducer head is moved over the selected track sector or clusteron the media and the voltage difference is monitored for change. As theheater power is increased, the close point of the transducer head isbrought closer to the media. The voltage difference is used to detectwhen the close point is brought in close proximity and/or in contactwith the media.

As the heater power is linearly increased, the voltage difference willeventually increase as well, indicating that the transducer head is inclose proximity to the media. In a first recordation operation 1040,when the voltage difference exceeds a predefined threshold, a head-mediaproximity event is recorded. Further, as the heater power is increasedfurther, the increasing voltage difference will eventually reverse andbegin to decline, indicating that the transducer head is in contact withthe media. In a second recordation operation 1050, when the voltagedifference reverses direction and declines from a peak magnitude, ahead-media contact event is recorded.

The first recordation operation 1040 and second recordation operation1050 are used to set transducer head fly height while the transducerhead is flying over the selected track sector or sectors. In oneimplementation, the fly height is set at a heater power within thevoltage difference recorded between the head-media proximity event andthe head-media contact event. Moving operation 1020, heating operation1030, first recordation operation 1040, and second recordation operation1050 may be repeated for each track sector or cluster on the mediaand/or varying operating conditions of the transducer head. As a result,the transducer head fly height (or head-media spacing (HMS)) can bespecifically calibrated for reading and/or writing data to/from allportions of the media. For example, power supplied to a heater using athermal actuation controller may be varied to maintain a selected flyheight over all portions of the media.

In some implementations, the proximity and/or contact detectionoperations described with regard to FIG. 10 are performed once duringcommissioning of the data storage device to map surface contours of themedia. The mapped surface contours are used to set fly height of thetransducer head. In other implementations, the proximity and/or contactdetection operations are performed periodically, to set the fly heightof the transducer head. For example, the contact detection operationsmay be performed every time there is a significant change in elevationof the data storage device or every time the data storage device crashesdue to impact of the transducer head with the media. In yet anotherimplementation, the proximity and/or contact detection operations arerepeated iteratively during drive operation to monitor HMS and adjustthe heater power to maintain a desired HMS. In an implementation such asthat depicted in FIGS. 7 and 9, the aforementioned operations 1000 maybe used for proximity/contact detection of the transducer head with themedia as well as laser power detection as detailed in operations 1100.

While the aforementioned operations 1000 specifically refer to measuringa difference between resistance values of two temperature sensors thatyields a voltage difference, the presently disclosed technology mayutilize only one temperature sensor to detect laser output, heateroutput, ambient drive temperature, write coil output, reader current,and/or proximity/contact of the transducer head with the media. Further,the resistance values of the two temperature sensors may be either addedor subtracted from one another to yield a noise-adjusted laser output,heater output, ambient drive temperature, write coil output, readercurrent, and/or proximity/contact of the transducer head with the media.

FIG. 11 illustrates example operations 1100 for detecting light outputin a HAMR transducer head using transducer head temperature monitoring.For example, the operations 1100 may apply to the HAMR transducer head202, 702, & 802 implementations depicted in FIGS. 2A, 2B, 7, & 8. In oneimplementation, a HAMR transducer head for heat-assisted reading and/orwriting data from/to the media is equipped with two resistancetemperature sensors, one near a light source (e.g., a laser diode,waveguide, and/or near-field transducer) and the other a known distanceaway from the light source. In a calibration operation 1110, currentapplied to one or both of the resistance temperature sensors in adifferential resistance circuit is calibrated to yield a voltagedifference of zero across the resistance temperature sensors when theresistance temperature sensors are at the same temperature. In analternative implementation, the current applied to one or bothresistance temperature sensors is calibrated to yield a known non-zerovoltage difference across the resistance temperature sensors.

In yet another implementation, a number of known factors are responsiblefor temperature variations in a HAMR transducer head (e.g., laseroutput, heater output, ambient drive temperature, write coil output,reader current, and proximity/contact of the transducer head with themedia). At least a laser diode, a heater, a write coil, a reader, and aclose point of the transducer head with the media are referred to hereinas a heat variation sources. At least the laser output (in a HAMRimplementation), heater output, ambient drive temperature, write coiloutput, reader current, proximity/contact of the transducer head withthe media are referred to herein as performance metrics. In thecalibration operation 1110, one or more of the known factors fortemperature variation are mapped to determine their contribution tovoltage difference across the resistance temperature sensors duringexpected normal operation of the transducer head or HAMR transducerhead.

Laser output directly affects the recording performance in a HAMRtransducer head. In applying operation 1120, power is applied to thelight source (e.g., a laser diode) during a recording operation. In oneimplementation, the light source is capable of affecting the temperatureof the resistance temperature sensor near the light source byapproximately 0.4 degrees Celsius. The initial power input into thelight source may be a preset value known to be close to a desired lightoutput. In a detecting operation 1130, a detected voltage difference isused to determine an actual light output of the light source to themedia. In a feedback operation 1140, the actual light output is comparedto a desired light output and the power applied to the light source ischanged to achieve the desired light output. In one implementation,operations 1120, 1130, & 1140 are repeated iteratively during driveoperation to monitor light output and update the power is applied to thelight source to maintain a desired light output. In anotherimplementation, operations 1120, 1130, & 1140 are performed once duringcommissioning of the drive to map light output to power is applied tothe light source. The mapped correlation between light output and powerinput is used to set power applied to the light source in a variety ofconditions. In other implementations, the contact detection operationsare performed periodically, to map light output to power is applied tothe light source.

While the aforementioned operations 1100 specifically refer to measuringa difference between resistance values of two temperature sensors thatyields a voltage difference, the presently disclosed technology mayutilize only one temperature sensor to detect laser output, heateroutput, ambient drive temperature, write coil output, reader current,and/or proximity/contact of the transducer head with the media. Further,the resistance values of the two temperature sensors may be either addedor subtracted from one another to yield a noise-adjusted laser output,heater output, ambient drive temperature, write coil output, readercurrent, and/or proximity/contact of the transducer head with the media.

The embodiments of the invention described herein may be implemented aslogical steps in one or more computer systems. The logical operations ofthe present invention are implemented (1) as a sequence ofprocessor-implemented steps executing in one or more computer systemsand (2) as interconnected machine or circuit modules within one or morecomputer systems. The implementation is a matter of choice, dependent onthe performance requirements of the computer system implementing theinvention. Accordingly, the logical operations making up the embodimentsof the invention described herein are referred to variously asoperations, steps, objects, or modules. Furthermore, it should beunderstood that logical operations may be performed in any order, unlessexplicitly claimed otherwise or a specific order is inherentlynecessitated by the claim language.

The above specification, examples, and data provide a completedescription of the structure and use of exemplary embodiments of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended. Furthermore, structuralfeatures of the different embodiments may be combined in yet anotherembodiment without departing from the recited claims.

1. A transducer head comprising: two temperature sensors at twodisparate distances from a heat variation source on the transducer head,wherein a difference between temperatures of each of the two temperaturesensors indicates a performance metric of the transducer head.
 2. Thetransducer head of claim 1, wherein the heat variation source is a closepoint of the transducer head with a media and the performance metric isproximity of the transducer head to the media at the close point.
 3. Thetransducer head of claim 1, wherein the heat variation source is aheat-assisted magnetic recording light source and the performance metricis light output from the heat-assisted magnetic recording light source.4. The transducer head of claim 3, wherein the light source is one ormore of a laser diode, waveguide, and a near-field transducer.
 5. Thetransducer head of claim 1, wherein the heat variation source is a closepoint of the transducer head with a media and the performance metric iscontact of the transducer head with the media at the close point.
 6. Thetransducer head of claim 1, wherein each of the temperature sensors areresistance temperature sensors and the temperatures of each of the twotemperature sensors are measured as resistance values and the differencebetween temperatures of each of the two temperature sensors is measuredas a voltage.
 7. The transducer head of claim 1, further comprising: aheater configured to bring a close point of the transducer head with themedia closer to the media.
 8. The transducer head of claim 7, whereinheater power changes fly height or maintains a selected fly height asthe transducer head flies over the media.
 9. The transducer head ofclaim 7, wherein the heater is controlled by a thermal actuationcontroller that modulates power to the heater at a known frequency. 10.The transducer head of claim 1, wherein a current modulator modulatescurrent applied to each of the temperature sensors at a known frequency.11. A method of detecting proximity of a transducer head to a mediacomprising: measuring a difference between temperatures of each of twotemperature sensors on a transducer head at two disparate distances froma close point of the transducer head indicating proximity of the closepoint to a media.
 12. The method of claim 11, wherein the differencebetween temperatures of each of the two temperature sensors furtherindicates contact of the transducer head with the media at the closepoint.
 13. The method of claim 11, further comprising: bringing theclose point of the transducer head closer to the media while performingthe measuring operation.
 14. The method of claim 11, further comprising:adjusting heater power to change fly height or maintain a selected flyheight as the transducer head flies over the media.
 15. The method ofclaim 11, further comprising: modulating power applied to one or more ofa heater on the transducer head and each of the two temperature sensorsat a known frequency.
 16. A method of detecting light output in a heatassisted magnetic recording (HAMR) transducer head comprising: applyingpower to a light source within the HAMR transducer head; measuring afirst resistance change at a first temperature sensor at a firstdistance from the light source; measuring a second resistance change ata second temperature sensor at a second distance from the light source,wherein the second distance is greater than the first distance; anddetecting light output of the light source by measuring a voltagedifference across the first and second temperature sensors.
 17. Themethod of claim 16, wherein the first temperature sensor and the secondtemperature sensor are positioned on opposite sides of a return polewithin the HAMR transducer head.
 18. The method of claim 16, wherein thefirst temperature sensor is at a first distance from a light pathrunning from the light source to a media and the second temperaturesensor is at a second distance from the light path, wherein the seconddistance is greater than the first distance.
 19. The method of claim 16,further comprising: adjusting the power to the light source to achieve adesired light output of the light source.
 20. The method of claim 16,further comprising: modulating power applied to one or more of a heateron the HAMR transducer head and each of the two temperature sensors at aknown frequency.